code: def which(program):
      try:
          return subprocess.check_output(
              "which " + program, shell=True
          ).strip()
      except subprocess.CalledProcessError:
          return None
  
file_path: DALI/dali_tf_plugin/dali_tf_plugin_utils.py
imports: import subprocess
  import os
  import re
  import sys
  import fnmatch
  from distutils.version import StrictVersion
label_desc: Use image node_id 7 for calling a global function with example usage: which(program) and returns: subprocess, None